Single-walled carbon nanotube and aligned single-walled carbon nanotube bulk structure, and their production process, production apparatus and application use

ABSTRACT

This invention provides an aligned single-layer carbon nanotube bulk structure, which comprises an assembly of a plurality of aligned single-layer carbon nanotube and has a height of not less than 10 μm, and an aligned single-layer carbon nanotube bulk structure which comprises an assembly of a plurality of aligned single-layer carbon nanotubes and has been patterned in a predetermined form. This structure is produced by chemical vapor deposition (CVD) of carbon nanotubes in the presence of a metal catalyst in a reaction atmosphere with an oxidizing agent, preferably water, added thereto. An aligned single-layer carbon nanotube bulk structure, which has realized high purify and significantly large scaled length or height, its production process and apparatus, and its applied products are provided.

TECHNICAL FIELD

The present invention relates to a carbon nanotube (CNT) and an alignedsingle-walled carbon nanotube bulk structure, as well as theirproduction process, production apparatus and application use and, morespecifically, it relates to a carbon nanotube and an alignedsingle-walled carbon nanotube bulk structure attaining high purity, highspecific surface area, large scale, and patterning, not found so far,and their production process, apparatus, and use.

BACKGROUND ART

For carbon nanotubes (CNT) for which development of functional materialshas been expected as new electronic device materials, optical devicematerials, conductive materials, bio-related materials, etc., studieshave been progressed earnestly for yield, quality, use, productivity,production process, etc.

One of methods for producing carbon nanotubes includes a chemical vapordeposition (CVD) method (hereinafter also referred to as a CVD method)and the method has attracted attention as being suitable to masssynthesis. The CVD method has a feature of bringing a carbon compound asa carbon source into contact with fine metal particles as a catalyst ata high temperature of about 500° C. to 1,000° C., and various variationsare possible depending on the kind and the arrangement of the catalyst,kinds of carbon compounds, and conditions and production ofsingle-walled carbon nanotube (SWCNT) and multi-walled carbon nanotube(MWCNT) is possible. Further, it has an advantage capable of growing bydisposing the catalyst on a substrate.

However, in the production of the carbon nanotube according to theexistent CVD method, since the catalyst or by-products intrude into theformed carbon nanotube, purifying treatment of applying various chemicaltreatments have been necessary in order to obtain a highly pure carbonnanotube from the product. The purification treatment includes aplurality of complicate and expensive processes, for example, an acidtreatment in combination, and required considerable skills and increasein the cost of obtained products. Further, even when such purificationtreatment is applied, the purity is restricted to about 90 to 94 mass %and it was difficult to obtain a single-walled carbon nanotube at highpurity of 98 mass/% or more (Nanoletters 2, 385 (2002)). Further,chemical and physical properties of the carbon nanotube often changed inpurification making it difficult to easily obtain carbon nanotubesalways at a determined quality.

Further, the growth of the carbon nanotubes by the existent CVD methodinvolved a problem that the activity lifetime of the metal catalyst wasshort, the activity was degraded in several seconds to several tensseconds and the growth rate of the carbon nanotube was not so great,which hindered the productivity.

With the situations described above, it has been proposed a method ofcontrolling the activity of the iron catalyst and the growth of thecarbon nanotube by preparing a catalyst by dipping a substrate in anaqueous mixed solution of FeCl₃ and hydroxylamine (Hee Cheul Choi, etal., NANO LETTERS, Vol. 3, No. 2, 157-161 (2003)).

However, with all such a proposal, extension of the lifetime of thecatalyst activity and increase in the growth rate have not yet beensatisfactory also with a practical point of view at present.

On the other hand, among the carbon nanotubes, single-walled carbonnanotubes have attracted attention as a material for nano-electronicdevices or nano-optical devices and energy storage in view of extremelyexcellent electrical property (extremely high maximum current density),thermal property (heat conductivity comparable with diamond), opticalproperty (light emission at an optical communication band wavelength),hydrogen storing performance, and metal catalyst supporting performance.In a case of effectively utilizing the single-walled carbon nanotube asthe material for the nano-electronic devices, nano-optical devices,energy storage, etc., it is desired that aligned single-walled carbonnanotubes form a bulk structure in the form of an aggregate comprisingaligned single-walled carbon nanotubes gathered in plurality, and thebulk structure provides electric, electronic, optical, and like otherfunctionality. Further, such carbon nanotube bulk structures aredesirably aligned in a predetermined direction, for example, as invertical alignment, and the length (height) is desirably large scaled.As bulk structures in which a plurality of vertically alignedsingle-walled carbon nanotubes are gathered reported so far, those witha height reaching 4 μm have been reported (Chem. Phys. Lett. vol. 385,p. 298 (2004)).

By the way, for applying the vertically aligned single-walled carbonnanotubes for nano-electronic devices, nano-optical devices or energystorage in practical use, a further large scale is necessary.

Further, those having a plurality of vertically aligned carbon nanotubesformed into the bulk structure and patterned are extremely suitable tothe application use for the nano-electronic devices, nano-opticaldevices, or energy storage as described above. However, while patterninghas been attained in some multi-walled carbon nanotubes (Science 283,412 (1999)), attainment of patterning for the single-walled carbonnanotubes has not yet been reported.

Compared with the multi-walled carbon nanotube, since the single-walledcarbon nanotube is excellent in properties such as more excellentstrength property, bending property, flexing property, higher opticaltransmittance, larger specific surface area, more excellent electronemitting property, more excellent electric conductivity and, further,presence of both semiconductors and metals while the multi-walled carbonnanotube is formed of a metal, it has been expected that when suchvertically aligned single-walled carbon nanotube bulk structure isformed, application use to nano-electronic device, nano-optical device,energy storage, etc. will be increased outstandingly. However, thesingle-walled carbon nanotubes tend to be adhered intensely to eachother because of a strong Van der Waals force and constitute adisordered and non-aligned bulk structure, for example, duringpurification for removing impurities and re-construction of once formednot-order and not-alignment bulk structure is extremely difficult, forexample, due to the difficulty in dispersing the single-walled carbonnanotubes in a solution and, with the reasons, such a bulk structure hasnot yet been obtained at present.

DISCLOSURE OF THE INVENTION

With background described above, the present invention has an object toprovide a carbon nanotube at high purity and high specific surface area(particularly, aligned single-walled carbon nanotube bulk structure) notfound so far, as well as a production process and an apparatustherefore.

Further, another object of the present invention is to extend the lifeof a metal catalyst, realize the growth of a carbon nanotube at highgrowth rate efficiently and by simple and convenient means without usingspecial organic materials such as hydroxylamine as in the proposedmethod described above, and provide a carbon nanotube also excellent inthe mass productivity, as well as production process and apparatustherefor.

Further, other object of the present invention is to provide an alignedsingle-walled carbon nanotube bulk structure at a high purity, having ahigh specific surface area, and attaining an outstandingly large-scaledlength or height, as well as a production process and an apparatustherefor.

Further, other object of the present invention is to provide an alignedsingle-walled carbon nanotube bulk structure attaining patterning, aswell as a production process and an apparatus therefor.

Further, other object of the present invention is to apply a carbonnanotube at the high purity and high specific surface area, and thealigned single-walled carbon nanotube bulk structure attaining the highpurity and high specific surface area, an outstandingly large-scaledlength or height, as well as the aligned single-walled carbon nanotubebulk structure attaining the patterning described above tonano-electronic devices, nano-optical devices or energy storage.

This application provides the following inventions for solving theproblems described above.

(1) A single-walled carbon nanotube, wherein the purity is 98 mass % orhigher.

(2) A single-walled carbon nanotube according to the above (1), whereinthe purity is 99 mass % or higher.

(3) A single-walled carbon nanotube according to the above (1) or (2),wherein the purity is 99.9 mass % or higher.

(4) A not-opened single-walled carbon nanotube, wherein the specificsurface area is 600 m²/g or more and 1,300 m²/g or less.

(5) A not-opened single-walled carbon nanotube according to any one ofthe above (1) to (3), wherein the specific surface area is 600 m²/g ormore and 1,300 m²/g or less.

(6) A not-opened single-walled carbon nanotube according to the above(4) or (5), wherein the specific surface area is 800 m²/g or more and1,200 m²/g or less.

(7) An opened single-walled carbon nanotube, wherein the specificsurface area is 1,600 m²/g or more and 2,500 m²/g or less.

(8) An opened single-walled carbon nanotube according to any one of theabove (1) to (3), wherein the specific surface area is 1,600 m²/g ormore and 2,500 m²/g or less.

(9) An opened single-walled carbon nanotube according to the above (7)or (8), wherein the specific surface area is 1,800 m²/g or more and2,300 m²/g or less.

(10) A single-walled carbon nanotube according to any one of the above(1) to (9), wherein it is aligned.

(11) A single-walled carbon nanotube according to any one of the above(1) to (10), wherein it is vertically aligned on a substrate.

(12) A process for producing a carbon nanotube by a method of chemicallyvapor depositing (CVD) a carbon nanotube under the presence of a metalcatalyst, wherein an oxidizing agent is added to a reaction atmosphere.

(13) A production process for a carbon nanotube according to the above(12), wherein the oxidizing agent is water vapor.

(14) A production process for a carbon nanotube according to the above(13), wherein 10 ppm or more and 10,000 ppm or less of water vapor areadded.

(15) A production process for a carbon nanotube according to the above(13) or (14), wherein water vapor is added at a temperature of 600° C.or higher and 1,000° C. or lower.

(16) A production process for a carbon nanotube according to any one ofthe above (12) to (15), wherein the obtained carbon nanotube issingle-walled.

(17) A production process for a carbon nanotube according to any one ofthe above (12) to (16), wherein vertically aligned carbon nanotube isgrown on the substrate surface with a catalyst being disposed on thesubstrate.

(18) A production process for a carbon nanotube according to any one ofthe above (12) to (17) characterized by obtaining a carbon nanotube witha length of 10 μm or more.

(19) A production process for a carbon nanotube according to any one ofthe above (12) to (18) characterized by obtaining a carbon nanotube witha length of 10 μm or more and 10 cm or less.

(20) A production process for a carbon nanotube according to any one ofthe above (12) to (19), wherein carbon nanotube, after the growth, canbe separated from the catalyst or the substrate without being exposed toa solution and a solvent.

(21) A production process for a carbon nanotube according to any one ofthe above (12) to (20), wherein a carbon nanotube at a purity of 98 mass% or higher is obtained.

(22) A production process for a carbon nanotube according to any one ofthe above (12) to (21), wherein a carbon nanotube at a purity of 99 mass% or higher is obtained.

(23) A production process for a carbon nanotube according to any one ofthe above (12) to (22), wherein a carbon nanotube at a purity of 99.9mass % or higher is obtained.

(24) A production process for a carbon nanotube according to any one ofthe above (12) to (23) characterized by obtaining a not-openedsingle-walled with a specific surface area of 600 m²/g or more and 1,300m²/g or less.

(25) A production process for a carbon nanotube according to any one ofthe above (12) to (24) characterized by obtaining a not-openedsingle-walled with a specific surface area of 800 m²/g or more and 1,200m²/g or less.

(26) A production process for a carbon nanotube according to any one ofthe above (12) to (23) characterized by obtaining an openedsingle-walled with a specific surface area of 1,600 m²/g or more and2,500 m²/g or less.

(27) A production process for a carbon nanotube according to any one ofthe above (12) to (23) and (26) characterized by obtaining an openedsingle-walled with a specific surface area of 1,800 m²/g or more and2,300 m²/g or less.

(28) An aligned single-walled carbon nanotube bulk structurecharacterized by comprising a plurality of aligned single-walled carbonnanotubes with the height of 10 μm or more.

(29) An aligned single-walled carbon nanotube bulk structure accordingto the above (28), wherein the height is 10 μm or more and 10 cm orless.

(30) An aligned single-walled carbon nanotube bulk structure accordingto the above (28) or (29), wherein the purity is 98 mass % higher.

(31) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (28) to (30), wherein the purity is 99 mass %higher.

(32) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (28) to (31), wherein the purity is 99.8 mass/%higher.

(33) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (28) to (32), wherein the specific surface areais 600 m²/g or more.

(34) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (28) to (33), wherein the specific surface areais 800 m²/g or more and 2,500 m²/g or less.

(35) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (28) to (34), wherein the specific surface areais 1,000 m²/g or more and 2,300 m²/g or less.

(36) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (28) to (32) characterized by comprisingnot-opened single-walled carbon nanotubes with the specific surface areaof 600 m²/g or more and 1,300 m²/g or less.

(37) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (28) to (32), and (36) characterized bycomprising not-opened single-walled carbon nanotubes with the specificsurface area of 800 m²/g or more and 1,200 m²/g or less.

(38) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (28) to (32) characterized by comprising openedsingle-walled carbon nanotubes with the specific surface area of 1,600m²/g or more and 2,500 m²/g or less.

(39) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (28) to (32), and (38) characterized bycomprising opened single-walled carbon nanotube with the specificsurface area of 1,800 m²/g or more and 2,300 m²/g or less.

(40) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (28) to (39) characterized by having anisotropyin at least one of optical characteristics, electric characteristics,mechanical characteristics, magnetic characteristics, and thermalanisotropy between the alignment direction and direction verticalthereto.

(41) An aligned single-walled carbon nanotube bulk structure accordingto the above (40), wherein the magnitude of the anisotropy between thealignment direction and the direction vertical thereto is such that alarger value is 1:3 or more relative to the smaller value.

(42) An aligned single-walled carbon nanotube bulk structure accordingto the above (40) or (41), wherein the magnitude of the anisotropybetween the alignment direction and the direction perpendicular theretois such that a larger value is 1:5 or more relative to the smallervalue.

(43) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (40) to (42), wherein the magnitude of theanisotropy between the alignment direction and the direction verticalthereto is such that a larger value is 1:10 or more relative to thesmaller value.

(44) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (28) to (43), wherein it can be obtained with noexposure to a solution and a solvent.

(45) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (28) to (44), wherein the shape of the bulkstructure is patterned into a predetermined shape.

(46) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (28) to (45) characterized by vertical alignmenton the substrate.

(47) An aligned single-walled carbon nanotube bulk structure accordingto any one of the above (28) to (46), wherein the bulk structure is athin film.

(48) A process for producing an aligned single-walled carbon nanotubebulk structure patterning a metal catalyst on a substrate and chemicallyvapor depositing (CVD) a plurality of single-walled carbon nanotubes soas to be aligned in a predetermined direction to the substrate surfaceunder the presence of the metal catalyst to form a bulk structure,wherein an oxidizing agent is added to a reaction atmosphere.

(49) A production process for an aligned single-walled carbon nanotubebulk structure according to the above (48), wherein the oxidizing agentis water vapor.

(50) A production process for an aligned single-walled carbon nanotubebulk structure according to the above (49), wherein 10 ppm or more and10,000 ppm or less of water vapor is added.

(51) A production process for an aligned single-walled carbon nanotubebulk structure according to the above (49) or (50), wherein water vaporare added at a temperature of 600° C. or higher and 1,000° C. or lower.

(52) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (51)characterized by obtaining a bulk structure with a height of 10 μm ormore.

(53) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (52)characterized by obtaining a bulk structure with a height of 10 μm ormore and 10 cm or less.

(54) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (53), whereinthe shape of the bulk structure is controlled by the patterning of themetal catalyst and the growth of the carbon nanotube.

(55) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (54), whereinbulk structure, after the growth can be separated from the catalyst orthe substrate without being exposed to a solution and a solvent.

(56) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (55)characterized by obtaining a bulk structure at a purity of 98 mass % ormore.

(57) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (56)characterized by obtaining a bulk structure at a purity of 99 mass % ormore.

(58) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (57)characterized by obtaining a bulk structure at a purity of 99.9 mass %or more.

(59) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (58)characterized by obtaining a bulk structure with a specific surface areaof 600 m²/g or more.

(60) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (59)characterized by obtaining a bulk structure with a specific surface areaof 800 m²/g or more and 2,500 m²/g or less.

(61) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (60)characterized by obtaining a bulk structure with a specific surface areaof 1,000 m²/g or more and 2,000 m²/g or less.

(62) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (58)characterized by obtaining a bulk structure comprising not-openedsingle-walled carbon nanotubes with a specific surface area of 600 m²/gor more and 1,300 m²/g or less.

(63) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (58), and (62)characterized by obtaining a bulk structure comprising not-openedsingle-walled carbon nanotubes with a specific surface area of 800 m²/gor more and 1,200 m²/g or less.

(64) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (58)characterized by obtaining a bulk structure comprising openedsingle-walled carbon nanotubes with a specific surface area of 1,600m²/g or more and 2,500 m²/g or less.

(65) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (58), and (64)characterized by obtaining a bulk structure comprising openedsingle-walled carbon nanotubes with a specific surface area of 1,800m²/g or more and 2,300 m²/g or less.

(66) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (65)characterized by having anisotropy in at least one of opticalcharacteristics, electric characteristics, mechanical characteristics,magnetic characteristics, and thermal anisotropy between the alignmentdirection and direction vertical thereto.

(67) A production process for an aligned single-walled carbon nanotubebulk structure according to the above (66), wherein the magnitude of theanisotropy between the alignment direction and the direction verticalthereto is such that a larger value is 1:3 or more relative to thesmaller value.

(68) A production process for an aligned single-walled carbon nanotubebulk structure according to the above (66) or (67), wherein themagnitude of the anisotropy between the alignment direction and thedirection vertical thereto is such that a larger value is 1:5 or morerelative to the smaller value.

(69) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (67) and (68), whereinthe magnitude of the anisotropy between the alignment direction and thedirection vertical thereto is such that a larger value is 1:10 or morerelative to the smaller value.

(70) A production process for an aligned single-walled carbon nanotubebulk structure according to any one of the above (48) to (69), whereinthe alignment in the predetermined direction is vertical alignment.

(71) A separation apparatus of separating single-walled carbon nanotubesaccording to any one of the above (1) to (11), or aligned single-walledcarbon nanotube, bulk structure according to any one of the above (28)to (47) from at least either of a substrate and a catalyst, which isprovided with cutting means or suction means.

(72) A production process for carbon nanotubes characterized by thecombination of a step of growing carbon nanotubes and a step of breakingby products that deactivate the catalyst.

(73) A production process for a carbon nanotube according to the above(72), wherein each of the steps is conducted in a gas phase or in aliquid phase.

(74) A carbon nanotube chemical vapor deposition apparatus characterizedby the provision of water vapor supply means.

(75) A heat dissipation material characterized by using a single-walledcarbon nanotube according to any one of the above (1) to (11), or analigned single-walled carbon nanotube bulk structure according to anyone of the above (28) to (47).

(76) A composite material characterized by containing a heat dissipationmaterial according to the above (75).

(77) An article characterized by having a heat dissipation materialaccording to the above (75).

(78) An article according to the above (77) comprising at least onemember selected from electric products, electronic products, opticalproducts, and mechanical products requiring heat dissipation.

(79) A heat conductive material characterized by using single-walledcarbon nanotubes according to any one of the above (1) to (11), or analigned single-walled carbon nanotube bulk structure according to anyone of the above (28) to (47).

(80) A composite material characterized by containing a heat conductoraccording to the above (79).

(81) An article characterized by the provision of a heat conductoraccording to the above (80).

(82) An article according to the above (81) comprising at least onemember selected from electric products, electronic products, opticalproducts, and mechanical products requiring heat conduction.

(83) An electric conductor characterized by using single-walled carbonnanotubes according to any one of the above (1) to (11), or an alignedsingle-walled carbon nanotube bulk structure according to any one of theabove (28) to (47).

(84) A composite material characterized by containing an electricconductor according to the above (83).

(85) An article characterized by the provision of an electric conductoraccording to the above (83).

(86) An article according to the above (85) comprising at least onemember selected from electric products, electronic products, opticalproducts, and mechanical products requiring electro conductivity.

(87) A wiring characterized by using an electric conductor according tothe above (83).

(88) A wiring according to the above (87) wherein the wiring is a viawiring.

(89) An electronic part characterized by having the wiring according tothe above (87) or (88).

(90) An optical device using single-walled carbon nanotubes according toany one of the above (1) to (11), or an aligned single-walled carbonnanotube bulk structure according to any one of the above (28) to (47).

(91) An optical device according to the above (90), wherein the opticaldevice is a polarizer.

(92) A composite material characterized by containing an optical deviceaccording to the above (90) or (91).

(93) An optical product characterized by containing an optical deviceaccording to the above (90) or (91).

(94) A reinforcing material characterized by using single-walled carbonnanotubes according to any one of the above (1) to (11), or an alignedsingle-walled carbon nanotube bulk structure according to any one of theabove (28) to (47).

(95) A reinforcing material according to the above (94), whereinsingle-walled carbon nanotubes or an aligned single-walled carbonnanotube bulk structure is formed as a laminate.

(96) A composite material characterized by containing a reinforcingmaterial according to the above (94) or (95).

(97) A composite material according to the above (96), wherein at leastone member selected from metals, ceramics, and resins is used as thebase material.

(98) An electrode material characterized by using single-walled carbonnanotubes according to any one of the above (1) to (11), or an alignedsingle-walled carbon nanotube bulk structure according to any one of theabove (28) to (47).

(99) A composite material characterized by containing an electrodematerial according to the above (98).

(100) A battery characterized by using an electrode material accordingto the above (98) as an electrode.

(101) A battery according to the above (100), wherein the battery is atleast one member selected from secondary battery, fuel cell, and aircell.

(102) A capacitor or a super capacitor characterized by usingsingle-walled carbon nanotubes according to any one of claims (1) to(11), or an aligned single-walled carbon nanotube bulk structureaccording to any one claims (28) to (47) as an electrode material or aconstituent material.

(103) An electrode emission device characterized by using single-walledcarbon nanotubes according to any one of the above (1) to (11), or analigned single-walled carbon nanotube bulk structure according to anyone of the above (28) to (47).

(104) An electric field emission type display characterized by theprovision of an electron emission device according to the above (103).

(105) An absorbent characterized by using single-walled carbon nanotubesaccording to any one of the above (1) to (11), or an alignedsingle-walled carbon nanotube bulk structure according to any one of theabove (28) to (47).

(106) A gas occlusion material characterized by using single-walledcarbon nanotubes according to any one of the above (1) to (11), or analigned single-walled carbon nanotube bulk structure according to anyone of the above (28) to (47).

As has been described above, since the single-walled carbon nanotubesaccording to (first) to (11th) inventions of the application aresuppressed for the intrusion of the catalyst, by-products, etc.,improved in the purity and increased in the specific surface areacompared with existent single-walled carbon nanotubes, they areextremely useful in the application use to nano-electronic devices,nano-optical devices, energy storage, etc.

Further, in the method according to (12th) to (27th) inventions of theapplication, the single-walled carbon nanotubes according to (first) to(11th) inventions can be produced by extremely simple and convenientmeans of adding an oxidizing agent such as water vapor to the reactionsystem and, in addition, the multi-walled carbon nanotubes havingsimilar excellent properties can also be produced. Further, it ispossible to extend the lifetime of the metal catalyst, attain theeffective growth of carbon nanotubes at a high growth rate therebyenabling mass production, as well as the carbon nanotubes grown abovethe substrate can be peeled easily from the substrate or the catalyst.

Further, the aligned single-walled carbon nanotube bulk structuresaccording to (28th) to (47th) inventions of the application are formedby assembling a plurality of aligned single-walled carbon nanotubes,have electric, electronic, optical and like other functionality, aresuppressed with intrusion of the catalyst or by-products, enhanced forthe purity and increased for the surface area, as well as remarkablylarge-scaled for the height thereof, and they can be expected forapplication use to nano-electronic devices, nano-optical devices, energystorage, etc., as well as various other application uses. Further, amongthe aligned single-walled carbon nanotube bulk structures according tothe present invention, those patterned attain the patterning for thefirst time by the single-walled carbon nanotube assembly, and they werenot present so far and can be expected for the same application asdescribed above such as for nano-electronic devices, nano-opticaldevice, energy storage, etc., as well as various other application uses.

Further, by the method according to (48th) to (70th) inventions of theapplication, the aligned single-walled carbon nanotube bulk structuresaccording to (28th) to (47th) inventions can be produced by extremelysimple and convenient means is addition of water vapor, i,e., to thereaction system. Further, it is possible to extent the lifetime of themetal catalyst and attain the efficient growth of the alignedsingle-walled carbon nanotube bulk structure at high growth rate, andthe grown aligned single-walled carbon nanotube bulk structure can bepeeled easily from the substrate or the catalyst.

Further, by the separation apparatus according to (71st) invention ofthe application, the single-walled carbon nanotube, particularly, thealigned single-walled carbon nanotube bulk structure can be separatedfrom the substrate or the catalyst extremely simply and conveniently.

Further, by the method according to (72nd) or (73rd) inventions of theapplication, since the single-walled carbon nanotube and thesingle-walled aligned carbon nanotube can be produced efficientlywithout deactivating the catalyst for the long time and, in addition,not only the oxidation and combustion by the oxidizing agent but also byvarious kinds of processes such as chemical etching, plasmas, ionmilling, microwave irradiation, UV-ray, and irradiation can be adoptedand, in addition, any of gas phase or liquid phase process can beadopted, they have a great advantage of increasing the degree of freedomfor the selection of the production processes.

Further, by the apparatus according to (74th) invention of theapplication, the single-walled carbon nanotube and the single-walledaligned carbon nanotube described above can be mass produced at a highefficiency irrespective of the simple and convenient structure.

Further, according to (75th) to (106th) inventions of the application,various application uses can be attained such as for heat dissipationmaterials, heat conductors, electric conductors, optical devices,reinforcing materials, electrode materials, batteries, capacitors orsuper capacitors, electron emission devices, adsorbents, and gasstorages, as well as also to various other application uses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view for a separation apparatus used forseparating an aligned single-walled carbon nanotube bulk structure froma substrate or a catalyst.

FIG. 2 is a schematic view for a separation apparatus used forseparating an aligned single-walled carbon nanotube bulk structure froma substrate or a catalyst.

FIG. 3 is a graph showing a relation between the water addition amountand the height of the aligned single-walled carbon nanotube bulkstructure.

FIG. 4 is a graph showing a relation between the water addition amount,and the height of the aligned single-walled carbon nanotube, thecatalyst activity, and the catalyst life.

FIG. 5 is a view showing the state of a catalyst deactivated by productsobserved by an electron microscopic photograph.

FIG. 6 shows liquid nitrogen absorption/desorption isothermal curves ofaligned single-walled carbon nanotube bulk structures.

FIG. 7 shows height-weight and height-density curves of an alignedsingle-walled carbon nanotube bulk structure.

FIG. 8 is a graph showing the result of measurement for Raman spectrumof a carbon nanotube in an aligned single-walled carbon nanotube bulkstructure.

FIG. 9 is a graph showing the result of measurement for the sizedistribution of carbon nanotubes in an aligned single-walled carbonnanotube bulk structure.

FIG. 10 is a view schematically showing the outline of a productionprocess for a patterned vertically aligned single-walled carbon nanotubebulk structure.

FIG. 11 is a view showing, as a model, a way of controlling an alignedsingle-walled carbon nanotube bulk structure.

FIG. 12 is a schematic view of a production apparatus for asingle-walled carbon nanotube or an aligned single-walled carbonnanotube bulk structure.

FIG. 13 is a schematic view of a production apparatus for asingle-walled carbon nanotube or an aligned single-walled carbonnanotube bulk structure.

FIG. 14 is a schematic view of a production apparatus for asingle-walled carbon nanotube or an aligned single-walled carbonnanotube bulk structure.

FIG. 15 is a schematic view of a production apparatus for asingle-walled carbon nanotube or an aligned single-walled carbonnanotube bulk structure.

FIG. 16 is a schematic view of a production apparatus for asingle-walled carbon nanotube or an aligned single-walled carbonnanotube bulk structure.

FIG. 17 is a schematic view of a heat dissipation material using analigned single-walled carbon nanotube bulk structure and an electronicpart provided with the heat dissipation material.

FIG. 18 is a schematic view of a heat exchanger using a heat conductorusing an aligned single-walled carbon nanotube bulk structure.

FIG. 19 is a schematic view of an electronic part provided with viawirings using an aligned single-walled carbon nanotube bulk structure.

FIG. 20 is a schematic view of a polarizer using an alignedsingle-walled carbon nanotube bulk structure.

FIG. 21 is a view showing electron microscopic (SEM) photographic imagesshowing a production process for a reinforced single-walled carbonnanotube fiber using an aligned single-walled carbon nanotube bulkstructure, and a produced reinforced single-walled carbon nanotubefiber.

FIG. 22 is a schematic view of a super capacitor using an alignedsingle-walled carbon nanotube bulk structure as a constituent materialand an electrode material.

FIG. 23 is a schematic view of a hydrogen storage using an alignedsingle-walled carbon nanotube bulk structure.

FIG. 24 is a graph showing the state of the growth of a verticallyaligned single-walled carbon nanotube of Example 1.

FIG. 25 is a view of photographic images showing the state of the growthof a single-walled carbon nanotube produced by an existent CVD process.

FIG. 26 shows images formed by printing the photograph taken by adigital camera of a vertically aligned single-walled carbon nanotubebulk structure produced in Example 2.

FIG. 27 is a view showing electron microscopic (SEM) photographic imagesof a vertically aligned single-walled carbon nanotube bulk structureproduced in Example 2.

FIG. 28 is a view showing enlarged electron microscopic (SEM)photographic images of a vertically aligned of single-walled carbonnanotube bulk structure produced in Example 2.

FIG. 29 is a view showing photographic images of a vertically alignedsingle-walled carbon nanotube bulk structure produced in Example 2,separated from a substrate, dispersed in an aqueous solution, andobserved by an electron microscope (TEM).

FIG. 30 is a view showing enlarged photographic images of a verticallyaligned single-walled carbon nanotube bulk structure produced in Example2, separated from a substrate, dispersed in an aqueous solution, andobserved by an electron microscope (TEM).

FIG. 31 is a view, like FIG. 30, of an as-grown single-walled carbonnanotube produced by the existent CVD method.

FIG. 32 is a graph showing the result of thermogravimetric analysis of avertically aligned single-walled carbon nanotube bulk structure producedin Example 2.

FIG. 33 is a view showing photographic images, taken by a digitalcamera, showing the state of the vertically aligned single-walled carbonnanotube bulk structure before peeling.

FIG. 34 is a view, like FIG. 33, after peeling.

FIG. 35 is a view showing a peeled as-grown single-walled carbonnanotube products placed in a vessel.

FIG. 36 is a view showing electron microscopic (SEM) photographic imagesfor the shape of a vertical aligned single-walled carbon nanotube bulkstructure patterned into circular columnar shape.

FIG. 37 is a view showing images taken, by an electron microscope (SEM),for the state of a base of a bulk structure in FIG. 36.

FIG. 38 is a view showing enlarged images taken, by an electronmicroscope (SEM), for the state of a base of a bulk structure in FIG.36.

FIG. 39 is a view showing an example of an aligned single-walled carbonnanotube bulk structure by electron microscopic (SEM) photographicimages.

FIG. 40 is a view showing another example of an aligned single-walledcarbon nanotube bulk structure by electron microscopic (SEM)photographic images.

FIG. 41 is a view showing other example of an aligned single-walledcarbon nanotube bulk structure by electron microscopic (SEM)photographic images.

FIG. 42 is a view showing other example of an aligned single-walledcarbon nanotube bulk structure by electron microscopic (SEM)photographic images.

FIG. 43 is a view showing other example of an aligned single-walledcarbon nanotube bulk structure by electron microscopic (SEM)photographic images.

FIG. 44 is a view showing an images of an aligned bulk structureobserved by an electron microscope (SEM) from the frontal surface.

FIG. 45 is a view showing images for the corner of an example of analigned bulk structure observed by electron microscope (SEM).

FIG. 46 is a view showing a schematic experimental cell of a supercapacitor used in Example 6.

FIG. 47 shows a measured value for the charge/discharge characteristicof a super capacitor obtained in Example 6.

FIG. 48 is a graph of the charge/discharge characteristic of a lithiumcell obtained in Example 7.

FIG. 49 is a graph showing absorption/desorption isothermal curves of analigned single-walled carbon nanotube bulk structure measured in Example8.

FIG. 50 is a graph showing polarization dependency of the lighttransmittance of an aligned single-walled carbon nanotube bulk structureas a polarizer in Example 9.

FIG. 51 is a graph showing polarization dependency of the lightabsorbancy of an aligned single-walled carbon nanotube bulk structureused in Example 9.

FIG. 52 is a graph showing the hydrogen storage characteristic of analigned single-walled carbon nanotube bulk structure as a gas storage inExample 10.

FIG. 53 is a graph showing measured data for the thermal diffusivity ofan aligned single-walled carbon nanotube bulk structure as a heatdissipation material in FIG. 11.

FIG. 54 is a graph showing the electric transport characteristic of analigned single-walled carbon nanotube bulk structure as an electricconductor in Example 12.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention has the features as described above and there willbe described embodiments thereof hereinafter.

At first, a single-walled carbon nanotubes according to (first) to(11th) inventions of the application will be described.

The single-walled carbon nanotube of the present invention has a featurein that the purity is 98 mass % or more, preferably, 99 mass % or moreand, more preferably, 99.9 mass % or more.

The purity referred to in the specification is represented by the mass %of the carbon nanotube in the product. The purity is measured by theresult of elemental analysis using fluorescence X-rays.

The single-walled carbon nanotube can be produced, for example, by themethod of (12th) to (27th) inventions described above. Then, theobtained single-walled carbon nanotube has the high purity as describedabove. The purity is 98 mass % or more, preferably, 99 mass % or moreand more preferably, 99.9 mass % or more. In a case of not conductingthe purification treatment the purity of the as-grown, single-walledcarbon nanotube coincides with the purity of the final product. Apurification treatment may be applied optionally.

Further, the single-walled carbon nanotube of the present invention isnot opened and has a specific surface area of 600 m²/g or more and 1,300m²/g or less, preferably, 600 m²/g or more and 1,300 m²/g or less and,more preferably, 800 m²/g or more and 1,200 m²/g or less, or opened andhas a specific surface area of 1,600 m²/g or more and 2,500 m²/g orless, more preferably, 1,600 m²/g or more and 2,500 m²/g or less and,further preferably, 1,800 m²/g or more and 2,300 m²/g or less. Thesingle-walled carbon nanotube having such an extremely large specificsurface area has not been present so far and can be obtained for thefirst time by the present invention.

Further, the single-walled carbon nanotube can be aligned and can bepreferably aligned vertically above the substrate.

The vertically aligned single-walled carbon nanotube according to thepresent invention is suppressed for the intrusion of the catalyst orby-products, etc. and highly purified, and the purity for the finalproducts has not been obtained so far. Further, in a case of the growthabove the substrate, it can be easily peeled from the substrate or thecatalyst.

As a method of peeling the single-walled carbon nanotube includes amethod of physical, chemical, or mechanical peeling from the substrateand, for example, a method of peeling using, electric field, magneticfield, centrifugal force, or surface tension; a method of mechanicallypeeling from the substrate directly; and a method of peeling from thesubstrate by using pressure or heat can be used. A simple peeling methodincludes a method of picking-up and peeling directly from the substrateby a tweezers. More suitably, it can be separated by cutting from thesubstrate using a thin blade such as a cutter blade. Further, it canalso be peeled by sucking from the substrate using a vacuum pump or acleaner. Further, the catalyst remains on the substrate after peelingand a vertically aligned single-walled carbon nanotube can be grownnewly by utilizing the same.

Accordingly, such a single-walled carbon nanotube is extremely useful inthe application use to nano-electronic devices, nano-optical devices,energy storage, etc.

FIG. 1 and FIG. 2 schematically show typical examples of the apparatusfor peeling and separating a single-walled carbon nanotube from asubstrate or a catalyst.

Next, a process of producing a carbon nanotube according to (12th) to(27th) inventions of the application will be described.

The inventions concern a process for producing a carbon nanotube by CVDmethod and the constituent factor has a feature in that a metal catalystis present in a reaction system and an oxidizing agent is added to areaction atmosphere.

For the carbon compound as the starting carbon source, hydrocarbons,among all, lower hydrocarbons such as methane, ethane, propane,ethylene, propylene, and acetylene can be used suitably in the samemanner as usual. One or two or more of them may be used and it may alsobe considered the use of an oxygen-containing compound with lower numberof carbon atoms such as lower alcohols, for example, methanol orethanol, acetone or carbon monoxide so long for this can be allowed asthe reaction condition.

Any reaction atmospheric gas can be used so long as it does not reactwith the carbon nanotube and is inert at a growth temperature andincludes, for example, helium, argon, hydrogen, nitrogen, neon, krypton,carbon dioxide, and chlorine, or a gas mixture of them and,particularly, helium, argon, hydrogen and a gas mixture thereof arepreferred.

Any pressure can be applied for the reaction atmosphere, so long as itis within a range of any pressure at which carbon nanotubes have beenproduced so far and it is preferably 10² Pa or higher and 10⁷ Pa (100atm) or lower, more preferably, 10⁴ Pa or higher and 3×10⁵ Pa (3 atm) orlower and, particularly preferably, 5×10 Pa or higher and 9×10 Pa orlower.

A metal catalyst is present in the reaction system described above andany catalyst can be used properly so long as it has been used so far forthe production of carbon nanotubes and includes, iron chloride thinfilm, and iron thin film, iron-molybdenum thin film, alumina-iron thinfilm, alumina-cobalt thin film, alumina-iron-molybdenum thin film,prepared by sputtering.

As the existent amount of the catalyst, it can be used within a range ofthe amount by which carbon nanotubes have been produced so far. In acase of using the iron metal catalyst, the thickness is preferably 0.1nm or more, and 100 nm or less, more preferably, 0.5 nm or more and 5 nmor less and, particularly preferably, 1 nm or more and 2 nm or less.

For disposing the catalyst, any appropriate method such as sputteringvapor deposition can be used so long as it is a method of disposing themetal catalyst with the thickness as described above. Further, a greatamount of single-walled carbon nanotubes can be produced simultaneouslyby utilizing patterning for the metal catalyst to be described later.

While the temperature during the growth by CVD method can be properlydetermined by considering the reaction pressure, and the kind of themetal catalyst, the starting carbon source and the oxidizing agent, itis desirably set to such a temperature range as the effect for theaddition of the oxidizing agent can be provided sufficiently. For themost desirable temperature range, the lower limit value is set to such atemperature that by-products of deactivating the catalyst, for example,amorphous carbon or graphite layer is removed by the oxidizing agent andthe upper limit value is set to such a temperature that main products,for example, carbon nanotubes are not oxidized by the oxidizing agent.Specifically, in a case of water, it is preferably from 600° C. orhigher and 1,000° C. or lower and, it is effectively 650° C. or higherand 900° C. or less. In a case of oxygen, it is 650° C. or lower,preferably, 550° C. or lower. In a case of carbon dioxide, it iseffectively 1,200° C. or lower and, more preferably, 1,100° C. or lower.

Then, the addition of the oxidizing agent as one of features in thepresent invention has an effect of improving the activity of thecatalyst during CVD growth reaction and extending the activity lifetime.By the synergistic effect, the carbon nanotubes formed is increasedgreatly as a result. FIG. 3 shows a graph for quantitatively evaluatingthe addition amount of the oxidizing agent (water), and the activity andthe lifetime of the catalyst (catalyst: iron thin film; starting gas:ethylene). It can be seen that the catalyst activity is improved greatlyand the catalyst lifetime is extended by the addition of the oxidizingagent (water). In a case of not adding water, the catalyst activity andthe catalyst lifetime are decreased by so much as quantitativeevaluation becomes extremely difficult.

FIG. 4 shows an example of a relation between the addition amount of theoxidizing agent (water) and the height of the vertically alignedsingle-walled carbon nanotube bulk structure (amount of formedsingle-walled carbon nanotube). It can be seen that the height of thevertically aligned single-walled carbon nanotube bulk structure isgreatly increased by the addition of the oxidizing agent (water). Thisshows that the single-walled carbon nanotube is formed more efficientlyby the addition of the oxidizing agent (water). One of the mostprominent features according to the present invention is that thecatalyst activity, the catalyst lifetime, and the height thereof as theresult thereof are increased remarkably by the addition of the oxidizingagent (water). The finding that the height of the vertically alignedsingle-walled carbon nanotube bulk structure increases remarkably wasnot known at all before the present invention, which is an epoch-makingmatter found for the first time by the inventors of the presentinvention.

While the function of the oxidizing agent added in the present inventionis not apparent at present, it may be considered as described below.

In the usual growth process for the carbon nanotube, the catalyst iscovered during the growth with by-products such as amorphous carbon orgraphite layer resulted during the growth, by which the catalystactivity is lowered, the lifetime is shortened and it is rapidlydeactivated. FIG. 5 shows high-resolution electron microscopic images ofa catalyst with which the growth of the carbon nanotube has been failed.The catalyst failed for the growth the carbon nanotube is completelycovered with by-products formed during the growth such as amorphouscarbon or graphite layer. The catalyst is deactivated when theby-products cover the catalyst. However, it is estimated that when theoxidizing agent is present, the by-products formed during the growthsuch as amorphous carbon or graphite layers are oxidized and convertedinto CO gas or the like and removed from the catalyst layer, by whichthe catalyst activity is enhanced, the catalyst lifetime is extendedand, as a result, the growth of the carbon nanotube promotesefficiently, and a vertically oriented single-walled carbon nanotubebulk structure with remarkably increased height is obtained.

As the oxidizing agent, water vapor, oxygen, ozone, hydrogen sulfide,acid-gas, as well as lower alcohols such as ethanol and methanol,oxygen-containing compounds with the less number of carbon atoms such ascarbon monoxide and carbon dioxide, and a gas mixture thereof are alsoeffective. Among them, water vapor, oxygen, carbon dioxide, and carbonmonoxide are preferred and, particularly, water vapor is usedpreferably.

The addition amount is not particularly restricted and may be a verysmall amount. For example, in a case of water vapor, it is usually 10ppm or more and 10,000 ppm or less, more preferably, 50 ppm or more and1,000 ppm or less and, further preferably, 200 ppm or more and 700 ppmor less. With a view point of preventing the degradation of the catalystand enhancement of the catalyst activity due to the addition of watrvapor, the addition amount in a case of water vapor is desirably withina range as described above.

By the addition of the oxidizing agent, the growth of the carbonnanotube which has been completed so far in about 2 min at the longestcontinues for several tens minutes and the growth rate increases by 100times or more and, further, 1,000 times or more compared with the usualcase.

While the method according to the present invention can producesingle-walled and multi-walled carbon nanotubes, it particularlyprovides an effect for the production of the single-walled carbonnanotube. Then, while description is to be made for the single-walledcarbon nanotube, it is identical also for the multi-walled carbonnanotube.

In the method according to the present invention, the catalyst isdisposed on the substrate and the single-walled carbon nanotubevertically aligned to the substrate surface can be grown. In this case,appropriate substrates can be used properly so long as they have beenused so far for the production of the carbon nanotubes and include, forexample, those described below.

(1) Metals and semiconductors such as iron, nickel, chromium,molybdenum, tungsten, titanium, aluminum, manganese, cobalt, copper,silver, gold, platinum, niobium, tantalum, lead, zinc, gallium,germanium, indium, gallium, germanium, arsenic, indium, phosphorus, andantimony; alloys thereof; and oxides of such metals and alloys.(2) Thin films, sheets, plates, powders and porous materials of themetals, alloys, and oxides described above.(3) Non-metals such as silicon, quartz, glass, mica, graphite anddiamond; ceramics, wafers and thin films thereof.

A preferred range for the height (length) of the vertically alignedsingle-walled carbon nanotube produced by the process according to thepresent invention is different depending on the application use, and thelower limit is, preferably, 10 μm and, more preferably, 20 μm and,particularly preferably, 50 μm. While the upper limit is notparticularly restricted, it is preferably 2.5 mm, further preferably, 1cm and, particularly preferably, 10 cm with a practical view point ofuse.

The single-walled carbon nanotube produced by the method according tothe present invention is remarkably different from single-walled carbonnanotubes produced by existent CVD method in view of the purity. Thatis, the single-walled carbon nanotube produced by the method accordingto the present invention is at a high purity of 98 mass % or higher,preferably, 99 mass % or higher and, more preferably, 99.9 mass % orhigher. In addition, in a case of the growth above the substrate, it canbe peeled easily from the substrate or the catalyst. As the method andthe apparatus for peeling the single-walled carbon nanotube, the methoddescribed previously is adopted.

The single-walled carbon nanotube produced by the method according tothe present invention may also be applied optionally with the samepurification treatment as in the usual case.

Further, the single-walled carbon nanotube produced by the methodaccording to the present invention includes those not opened and havingthe specific surface area of 600 m²/g or more and 1,300 m²/g or less,more preferably, 600 m²/g or more and 1,300 m²/g or less and, furtherpreferably, 800 m²/g or more and 1,200 m²/g or less, or those opened andhaving the specific surface area of 1,600 m²/g or more and 2,500 m²/g orless, more preferably, 1,600 m²/g or more and 2,500 m²/g or less and,further preferably, 1,800 m²/g or more and 2,300 m²/g or less, and ithas an extremely large specific surface area.

While the method according to the present invention requires means forsupplying the oxidizing agent, the reaction apparatus, the constitutionand the structure of the reaction furnace for CVD method are notrestricted particularly. Specific embodiments will be described later.

Next, aligned single-walled carbon nanotube bulk structures according to(28th) to (47th) inventions of the application will be described.

The aligned single-walled carbon nanotube bulk structures according to(28th) to (47th) inventions of the application have a feature incomprising a plurality of aligned single-walled carbon nanotubes, with aheight of 10 μm or more.

“Structure” referred to the specification of the application comprisesaligned single-walled carbon nanotubes gathered in plurality andprovides electric/electronic, optical and like other functionality. Thealigned single-walled carbon nanotube bulk structure can be produced forexample by the method of the (48th) to (70th) and (72nd) to (73rd)inventions described above.

The aligned single-walled carbon nanotube bulk structure has a purity of98 mass % or higher, more preferably, 99 mass % or higher, and,particularly preferably, 99.9 mass % or higher. In a case of notconducting the purification treatment, the purity of the as-grown,aligned single-walled carbon nanotube bulk structure coincides with thepurity for the final product. A purification treatment may optionally beconducted. The aligned single-walled carbon nanotube bulk structure canbe put to predetermined alignment and, preferably, can be alignedvertically above the substrate.

While a preferred range for the height (length) of the alignedsingle-walled carbon nanotube bulk structure according to the presentinvention is different depending on the application use, in a case whereit is used in a large scale, the lower limit is, preferably, 10 μm, morepreferably, 20 μm and, particularly preferably, 50 μm, and the upperlimit is, preferably, 2.5 μm, more preferably, 1 cm and, particularlypreferably, 10 cm.

As described above, the aligned single-walled carbon nanotube bulkstructure according to the present invention is suppressed for theintrusion of the catalyst or the by-products, etc. and improved for thehigh purity, and the purity as the final product was not found so far.

Further, since the aligned single-walled-carbon nanotube bulk structureaccording to the present invention is greatly large-scaled also for theheight, various application uses can be expected in addition to theapplication to nano-electronic devices, nano-optical devices, energystorage, etc. as to be described later.

Further, while the specific surface area of the aligned single-walledcarbon nanotube bulk structure according to the present invention isextremely large and a preferred value is different in accordance withthe application use thereof, it is 600 m²/g or more, more preferably,800 m²/g or more and 2,500 m²/g or less and, more preferably, 1,000 m²/gor more and 2,300 m²/g or less in a case of the application use forwhich a large specific surface area is desired. Further, thesingle-walled carbon nanotube bulk structure according to the presentinvention has a specific surface area of 600 m²/g or more and 1,300 m²/gor less, more preferably, 600 m²/g or more and 1,300 m²/g or less and,further preferably, 800 m²/g or more and 1,200 m²/g or less for thosenot opened. Further, the single-walled carbon nanotube bulk structureaccording to the present invention has a specific surface area of 1,600m²/g or more and 2,500 m²/g or less, preferably, 1,600 m²/g or more and2,500 m²/g or less and, further preferably, 1,800 m²/g or more and 2,300m²/g or less for those opened. The single-walled carbon nanotube bulkstructure having such an extremely large specific surface area has notbeen present in the usual case and can be obtained for the first timeaccording to the present invention.

The aligned single-walled carbon nanotube bulk structure having such alarge specific surface area has a significant advantage in variousapplication uses such as heat dissipation bodies, electrode materials,super capacitors, fuel cells, adsorbents, filters, actuators (artificialmuscles), sensors, humidity controllers, and heat insulating agents.

Measurement for the specific surface area can be carried out bymeasurement for adsorption-desorption isothermal curves. As an example,for 30 mg of an aligned single-walled carbon nanotube bulk structurejust after the growth (as-grown) was measured for theadsorption-desorption isothermal curves for liquid nitrogen at 77 K byusing BELSORP-MINI manufactured by Bel Japan Inc. (adsorptionequilibrium time: 600 sec). The total adsorption amount showed anextremely large value (1,650 m²/g) (see FIG. 6). When the specificsurface area was measured from the adsorption-desorption isothermalcurves, it was 110 m²/g. Further, a linear adsorption-desorptionisothermal curve was obtained in a relative pressure range of 0.5 orless and it can be seen therefrom that the carbon nanotubes are notopened in the aligned single-walled carbon nanotube bulk structure.

Further, in the aligned single-walled carbon nanotube bulk structureaccording to the present invention, for example, as shown in Example 8to be described later, its top end portion is opened and the specificsurface area can be increased more by applying an opening treatment. InExample 8, an extremely large specific surface area as large as 2,000m²/g can be attained. For the opening treatment, a treatment with oxygencan be used as a dry process. In a case that a wet process can be used,an acid treatment, specifically, a refluxing treatment with hydrogenperoxide or a cutting treatment with hydrochloric acid at hightemperature can be used. Further, the aligned single-walled carbonnanotube bulk structure applied with the opening treatment shows aconvex type absorption-desorption isothermal curves in a relativepressure region of 0.5 for less (see FIG. 49). It can be seen from thisthat carbon nanotubes in the aligned single-walled carbon nanotube bulkstructure are opened.

On the contrary, the specific surface area of the single-walled carbonnanotube is 524 m²/g, for example, in Nano Letters 2, p. 385-388 (2002),and 567 m²/g in Chemical Physics Letters 365, p 69-74 (2002), and thespecific surface area of the existent aligned multi-walled carbonnanotube bulk structure only shows the value of about 200 to 300 m²/g atmost (Journal of Colloid and Interface Science 277, p 35-42 (2004)).

From the foregoings, it can be seen that the known aligned single-walledcarbon nanotube bulk structure according to the present invention hasthe maximum specific surface area to be noted particularly among thesingle-walled carbon nanotubes reported so far in the state as grown orafter the opening treatment.

Accordingly, since the aligned single-walled carbon nanotube bulkstructure according to the present invention has an extremely largesurface area compared with existent one, it is extremely prospective asheat dissipation bodies, electrode materials, super capacitors, fuelcells, adsorbents, filters, actuators (artificial muscles), sensors,humidity controllers, heat insulating agent, etc.

Further, since the aligned single-walled carbon nanotube bulk structureaccording to the present invention has an alignment property, it showsanisotropy between the direction of alignment and the direction verticalthereto in at least one of optical property, electrical property,mechanical property, magnetic property, and thermal property. The degreeof anisotropy between the direction of alignment and the directionvertical thereto in the single-walled carbon nanotube bulk structure is,preferably, 1:3 or more, more preferably, 1:5 or more and, particularlypreferably, 1:10 or more. The upper limit value is about 1:100. Forexample, in the case of the optical property, such large anisotropyenables application to a polarizer by utilizing the polarizationdependency of the light absorbance, or light transmittance. Also for theanisotropy in other properties than described above, application tovarious articles such as heat exchangers, heat pipes, reinforcingmaterials etc. by utilizing the anisotropy thereof respectively.

Further, the aligned single-walled carbon nanotube bulk structuresaccording to the present invention show constant density even when theheight is different. Usually, the value falls within a range from 0.002to 0.2 g/cm³, which can be controlled by controlling the density of thecatalyst.

FIG. 7 shows an example for height-weight and height-density curves ofan aligned single-walled carbon nanotube bulk density. It can be seenfrom FIG. 7 that the weight of the aligned single-walled carbon nanotubebulk structure according to the present invention increase in proportionwith the height, and the density of the aligned single-walled carbonnanotube bulk structure is constant irrespective of the height (0.036g/cm³).

Accordingly, the aligned single-walled carbon nanotube bulk structureaccording to the present invention is an extremely homogeneous material,and application use as heat dissipation sheets, heat conduction sheets,and heat exchangers can be expected.

Further, in the example of the single-walled carbon nanotube bulkstructure according to the present invention, the content of thesingle-walled carbon nanotube (filament) shows an extremely high valueof 99.5% or more under electron microscopic observation.

Further, the single-walled carbon nanotube bulk structure according tothe present invention contains therein single-walled carbon nanotubes(filaments) of high quality.

The quality of the single-walled carbon nanotubes (filaments) in thealigned single-walled carbon nanotube bulk structure can be evaluated bymeasurement of the Raman spectrum. FIG. 8 shows an example for themeasurement of the Raman spectrum. From FIG. 8, a G-band having a sharppeak is observed at 1592 Kaiser and it can be seen that a graphitecrystal structure is present. Further, since the D-band is small, it canbe seen that a graphite layer with less defects at high quality ispresent. Further, on the side of a low wavelength, an RBM modeattributable to a plurality of single-walled carbon nanotubes isobserved and it can be seen that the graphite layer is a single-walledcarbon nanotube. From the foregoings, it has been confirmed thatsingle-walled carbon nanotubes at high quality are present in thesingle-walled carbon nanotube bulk structure according to the presentinvention.

Further, the size of the mono-carbon nanotube (filament) in thesingle-walled carbon nanotube bulk structure according to the presentinvention shows a broad size distribution from 0.8 to 6 nm, and thecenter size is from 1 to 4 nm. The size distribution and the center sizecan also be controlled by the preparation of the catalyst.

The size distribution of the single-walled carbon nanotube (filament)can be evaluated by a high-resolution electron microscope. That is, thesize distribution can be obtained by measuring the size on everysingle-walled carbon nanotubes from the electron microscopic photograph,preparing a histogram and conducting calculation based on the preparedhistogram. FIG. 9 shows an example for the evaluation of the sizedistribution. It has been confirmed from FIG. 9 that the single-walledcarbon nanotubes in the aligned single-walled carbon nanotube bulkstructure show a broad size distribution from 1 to 4 nm and the centersize is 3 nm.

It has been found that the size distribution is extremely largercompared with the center size of 1 nm for the single-walled nanotubeprepared by an existent HiPco method and 1.5 nm for the single-walledcarbon nanotube prepared by a laser abrasion method. A tube of a largesize has a large inner space and can include bio-molecules such as DNAwhich could not be included so far and has extremely high utility as anew composite material.

The aligned single-walled carbon nanotube bulk structure can incorporatedouble-walled or multi-walled carbon nanotubes or further more layers ofcarbon nanotubes within a range not deteriorating the function thereof.

Further, the aligned single-walled carbon nanotube bulk structureaccording to the present invention can be formed into a shape patternedto a predetermined shape. Those in which a plurality of alignedmulti-walled carbon nanotubes are aggregated and the shape is patternedto a predetermined shape were not present so far, which have beenattained for the first time according to the present invention. Thepatterning shape can be in various shapes such as thin film shape, aswell as a columnar shape, prismatic shape, or complicated shape. Thepatterning can be controlled by the method as will be described later.

Then, a process for producing an aligned single-walled carbon nanotubebulk structure according to (48th) to (70th) inventions of theapplication will be described.

The method according to the present invention concerns a method ofproducing an aligned single-walled carbon nanotube bulk structure by CVDmethod and the constituent factor comprises patterning a metal catalyston a substrate, and chemically vapor depositing (CVD) a plurality ofsingle-walled carbon nanotubes into a structure so as to be aligned in apredetermined direction to the substrate surface under the presence ofthe metal catalyst, in which an oxidizing agent is added to a reactionatmosphere. In this case, description is to be made mainly for the caseof patterning the aligned single-walled carbon nanotube bulk structure.FIG. 10 schematically shows the outline for the step of the productionprocess.

For the carbon compound as the starting carbon source, hydrocarbons,among all, lower hydrocarbons, for example, methane, ethane, propane,ethylene, propylene, acetylene, etc. can be used suitably in the samemanner as in the case of the (12th) to (27th) inventions describedabove. One or two or more of them may be used and it may be alsoconsidered the use of lower alcohols such as methanol and ethanol,acetone, and oxygen-containing compounds with a low number of carbonatoms such as carbon monoxide.

Any gas can be used for the reaction atmospheric so long as it does notreact with the carbon nanotube and is inert at a growth temperature andincludes, for example, helium, argon, hydrogen, nitrogen, neon, krypton,carbon dioxide, chlorine, or a gas mixture of them and, particularly,helium, argon, hydrogen and a gas mixture thereof are preferred.

Any pressure can be applied for the reaction atmosphere, within a rangeof pressure at which carbon nanotubes have been produced so far, and itis preferably 10² Pa or higher and 10⁷ Pa (100 atm) or lower, morepreferably, 10⁴ Pa or higher and 3×10⁵ Pa (3 atm) or lower and,particularly preferably, 5×10 Pa or higher and 9×10 Pa or lower.

The metal catalyst as described above is present in the reaction systemand any appropriate catalyst can be used so long as it has been used sofar for the production of the carbon nanotubes and includes, forexample, iron chloride thin film, and iron thin film, iron-molybdenumthin film, alumina-iron thin film, alumina-cobalt thin film, andalumina-iron-molybdenum thin film, prepared by sputtering.

As the existent amount of the catalyst, it can be used within a range ofthe amount with which the carbon nanotubes were produced so far and in acase, for example, of using the iron metal catalyst, the thickness is,preferably, 0.1 nm or more, and 100 nm or less, more preferably, 0.5 nmor more and 5 nm or less and, particularly preferably, 1 nm or more and2 nm or less. The area in which the catalyst is present can be setoptionally in accordance with the size of the structure to the produced.

As the patterning method for the catalyst, any appropriate method can beused so long as it is a method capable of directly or indirectlypatterning the metal catalyst, which may be a wet process or a dryprocess, and, for example, may be patterning by using a mask, patterningby using nano-imprinting, patterning by using soft lithography,patterning by using printing, patterning by using plating, andpatterning by using screen printing, patterning using lithography, aswell as a method of patterning other material to which the catalyst isadsorbed selectively on a substrate, and selectively adsorbing thecatalyst to other material thereby preparing a pattern. A preferredmethod includes patterning by using lithography, metal vapor depositionphotolithography using a mask, electron beam lithography, catalyst metalpatterning by an electron beam vapor deposition method using a mask, anda catalyst metal patterning by a sputtering method using a mask.

Also for the substrate, identical kinds of substrates with thosedescribed for the (12th) to (27th) inventions can be used.

Also for the temperature during the growth reaction by the CVD method,identical temperature conditions with those described for (12th) to(27th) inventions described above may be selected.

Then, addition of the oxidizing agent as one of greatest features in thepresent invention has an effect of enhancing the activity of thecatalyst during the CVD growth reaction and extending the activity lifeas described above.

As a result, formed carbon nanotubes increase remarkably by thesynergistic effect and an vertically aligned single-walled carbonnanotube bulk structure with the height being increased remarkably canbe obtained. The addition amount has no particular restriction but maybe a very small amount. While it is different depending on theproduction condition, in a case of water vapor, for example, it isusually 10 ppm or more and 10,000 ppm or less, more preferably, 50 ppmor more and 1,000 ppm or less and, further preferably, 200 ppm or moreand 700 ppm or less. The addition amount of the water vapor is desirablywithin the range as described above with a view point of preventing thedegradation of the catalyst and improving the catalyst activity due tothe water vapor addition.

By the addition of the oxidizing agent, the growth of the carbonnanotube, which was completed so far for about 2 min at the longest inusual case, continues for several tens minutes and the growth rateincrease 100 times or more and, further, 1,000 times or more comparedwith the usual case.

While the preferred range of the height (length) of the alignedsingle-walled carbon nanotube bulk structure produced by the methodaccording to the present invention is different in accordance with theapplication use, the lower limit is preferably 10 μm, more preferably,20 μnm, and, particularly preferably, 50 μm. While the upper limit hasno particularly restriction, it is preferably 2.5 mm, more preferably, 1cm and, particularly preferably, 10 cm.

The aligned single-walled carbon nanotube-bulk structure produced by themethod according to the present invention is remarkably different fromthe aligned single-walled carbon nanotube bulk structure produced by theexistent CVD method in view of the purity. That is, the alignedsingle-walled carbon nanotube-bulk structure produced by the methodaccording to the present invention is at a purity of 98 mass % orhigher, more preferably, 99 mass/% or higher and, particularlypreferably, 99.9 mass % or higher and, in addition, in a case beinggrown on the substrate, it can be peeled easily from the substrate orthe catalyst. As the peeling method, the same method as described in thecase of (12th) to (27th) inventions described above can be used.

The aligned single-walled carbon nanotube-bulk structure produced by themethod according to the present invention may be applied optionally withthe same purification treatment as usual.

Further, the aligned single-walled carbon nanotube-bulk structureproduced by the method according to the present invention is 600 m²/g ormore, more preferably, 800 m²/g or more and 2,500 m²/g or less and, morepreferably, 1,000 m²/g or more and 2,300 m²/g or less. Further, thesingle-walled carbon nanotube bulk structure according to the presentinvention has a specific surface area of 600 m²/g or more and 1,300 m²/gor less, more preferably, 600 m²/g or more and 1,300 m²/g or less, and,more preferably, 800 m²/g or more and 1,200 m²/g or less for those ofnot-opened structures. Further, the single-walled carbon nanotube bulkstructure according to the present invention has a specific surface areaof the 1,600 m²/g or more and 2,500 m²/g or less, more preferably, 1,600m²/g or more and 2,500 m²/g or less and, further preferably, 1,800 m²/gor more and 2,300 m²/g or less those of opened structures.

Further, in the method according to the present invention, the shape ofthe bulk structure can be controlled optionally depending on thepatterning of the metal catalyst and the growth of the carbon nanotube.FIG. 11 shows an example for the way of controlling by modeling.

This is an example of a thin-film shape bulk structure (structure may bereferred to as a bulk shape even when it is in a thin film shaperelative to the diametrical size of the carbon nanotube) in which thethickness is thin compared with the width and, the width can becontrolled to an optional length by the patterning of the catalyst, thethickness can also be controlled to an optional thickness by thepatterning of the catalyst, and the height can be controlled by thegrowth of each of the vertically aligned single-walled carbon nanotubesconstituting the structure. In FIG. 11, the orientation of thevertically aligned single-walled carbon nanotubes is shown by an arrow.

As a matter of course, the shape of aligned single-walled carbonnanotube-bulk structure produced by the method according to the presentinvention is not restricted to the thin-film shape and can be in variousshapes by the patterning of the catalyst and the control for the growthsuch as columnar shape, prismatic shape, or a complicated shape.

While it is necessary that the chemical vapor deposition (CVD) apparatusfor the carbon nanotube according to the present invention has means forsupplying the oxidizing agent, other constitutions and structures of thereaction apparatus and the reaction furnaces for the CVD method have noparticular restriction and any of known apparatus such as thermal CVDfurnace, thermal heating furnace, electric furnace, drying furnace,thermostatic vessel, atmospheric furnace, gas substitution furnace,muffle furnace, oven, vacuum heating furnace, plasma reaction furnace,microplasma reaction furnace, RF plasma reaction furnace,electromagnetic heating reaction furnace, microwave irradiation reactionfurnace, infrared ray irradiation heating furnace, UV-ray heatingreaction furnace, MBE reaction furnace, MOCVD reaction furnace, andlaser heating apparatus can be used.

Arrangement and constitution for the oxidizing agent supplying meanshave no particular restriction and they include supply as a gas or gasmixture, supply by evaporation of an oxidizing agent-containingsolution, supply by evaporization and liquefication of a solid oxidizingagent, supply by using an oxidizing agent atmosphere gas, supplyutilizing spray, supply utilizing high pressure or reduced pressure,supply utilizing injection, supply utilizing a gas stream, supply incombination of such means in plurality, etc., and it is adopted supplyby using bubbler, gasifier, mixer, stirrer, dilution device, sprayer,nozzle, pump, injection syringe, or compressor, or a system comprising aplurality of such equipments in combination.

Further, for supplying an extremely very small amount of the oxidizingagent under precise control, the apparatus may be provided with apurification device for removing the oxidizing agent from the startingmaterial gas or carrier gas and, in this case, the apparatus suppliesthe oxidizing agent in the amount controlled by any of the meansdescribed above to the starting gas or the carrier gas removed with theoxidizing agent in the subsequent stage. The method is effective in acase where the oxidizing effect is contained by a very small amount inthe starting gas or the carrier gas.

Further, for stably supplying the oxidizing agent under precise control,the apparatus may be provided with a measuring device for measuring theconcentration of the oxidizing agent and, in this case, a stable supplyof the oxidizing agent with less change with time may be carried out byfeeding back the measured value to the oxidizing agent flow controlmeans.

Further, the measuring apparatus may be an apparatus for measuring thesynthesis amount of the carbon nanotubes or, alternatively, it may be anapparatus for measuring by-products formed from the oxidizing agent.

Further, for synthesizing a great amount of carbon nanotubes, thereaction furnace may be provided with a system of supplying andrecovering substrates in plurality or continuously.

FIG. 12 to FIG. 16 schematically show examples of the CVD apparatus usedpreferably for practicing the method according to the present invention.

Then, the method of producing carbon nanotubes according to (72nd) to(73rd) inventions of the application will be described.

The method according to the present invention has a feature in combininga step of growth carbon nanotubes and a step of breaking by-productsthat deactivate the catalyst, for example, amorphous carbon or graphitelayers and conducting reaction under a gas phase or under a liquidphase.

The growth step means a step of growth crystals of a carbon nanotube.For the growth step, an existent carbon nanotube production steps isapplied as it is. That is, as an embodiment of the growth step, any ofexistent carbon nanotube production steps can be used and, for example,it includes an embodiment of the growth carbon nanotubes by decomposingthe starting carbon source on the catalyst in the chemical vapordeposition (CVD) apparatus.

The breaking step means a process of properly excluding by-products inthe carbon nanotube production step which deactivate the catalyst, forexample, amorphous carbon or graphite layer and not excluding the carbonnanotubes per se. Accordingly, for the breaking step, any process can beadopted so long as it excludes by-products in the carbon nanotubeproduction step, i.e., substances that deactivate the catalyst. Suchstep can include, for example, oxidation and combustion by the oxidizingagent, chemical etching, plasmas, ion milling, microwave irradiation,UV-ray irradiation, and breaking by quenching. Use of the oxidizingagent is preferred and, use of the water is particularly preferred.

The embodiment as a combination of the growth step and the breaking stepincludes, for example, simultaneous conduction of the growth step andthe breaking step, alternate conduction of the growth step and thebreaking step, or combination of a mode for emphasizing the growth stepand a mode of emphasizing the breaking step, etc.

As apparatus for practicing the method according to the presentinvention, any of the apparatus described above can be used.

By the combination of such steps, in the method according to the presentinvention, the single-walled carbon nanotube and the single-walledaligned carbon nanotube can be produced at a high efficiency withoutdeactivating the catalyst for a long time and, further, since variouskinds of versatile processes such as chemical etching, plasmas, ionmilling, microwave irradiation, UV-ray irradiation, and breaking byquenching can be adopted in addition to the oxidation and combustion bythe oxidizing agent can be adopted and, any of the gas phase or theliquid phase process can be adopted, it provides a great advantage ofincreasing the degree of freedom for selecting the production process.

Since the single-walled carbon nanotube, the aligned single-walledcarbon nanotubes comprising plural single-walled carbon nanotubes withthe height of 10 μm or more, and the aligned single-walled carbonnanotube bulk structure comprising plural single-walled carbon nanotubesand whose shape is patterned to a predetermined shape according to thepresent invention have various properties and characteristics such assuper high purity, super heat conductivity, high specific surface area,excellent electronic/electric properties, optical properties, supermechanical strength, and super high density, they can be applied tovarious technical fields and application uses. Particularly, thelarge-scaled vertically aligned bulk structure and the patternedvertically aligned bulk structure can be applied to the technical fieldsas described below.

(A) Heat Dissipation Material (Heat Dissipation Property)

Further higher rate and higher integration degree are demanded for theoperation performance of CPU as a heart of a computer of an articlerequiring heat dissipation, for example, electronic parts and the degreeof heat generation from CPU per se has been increased more and more, andit is said that a limit will be imposed on the improvement for theperformance of LSI in near future. Heretofore, in a case of heatdissipating for such heat generation density, carbon nanotubes alignedat random buried in a polymer has been known as a heat dissipationmaterial but it involves a problem of lacking in heat releasing propertyin the vertical direction. Since the large-scaled vertically alignedcarbon nanotube bulk structure according to the present invention showsa high heat releasing property and is vertically aligned at a highdensity in an elongate form, the heat dissipating property in thevertical direction can be enhanced outstandingly by utilizing it as theheat dissipating material, compared with the existent goods.

An example of the heat dissipating material is schematically shown inFIG. 17.

The heat dissipating material according to the present invention can beutilized not being restricted to electronic parts but to other variousarticles requiring heat dissipation, for example, as the heatdissipation material for electric products, optical products, andmechanical products.

(B) Heat Conductor (Heat Conduction Property)

The vertically aligned carbon nanotube bulk structure according to thepresent invention has a good heat conduction property. The verticallyaligned carbon nanotube bulk structure excellent in heat conductionproperty can provide a high heat conduction material by being formed asa heat conduction material as a composite material containing the sameand, in a case of application to a heat exchanger, drier, heat pipe,etc., can improve the performance thereof. In a case of applying such aheat conduction material to heat exchanger for aerospace use, the heatexchanging performance can be improved and the weight and volume can bereduced. Further, in a case of applying such a heat conduction materialto fuel cell cogeneration or micro gas turbine, it is possible toimprove the heat exchanger performance and improve the heat resistance.FIG. 18 schematically shows an example of a heat exchanger utilizing theheat conduction material.

(C) Electric Conductor (Electric Conductivity)

An electronic part, for example, a current integrated LSI has a layeredstructure. A via wiring means a vertical wiring between vertical layersinside LSI for which copper wirings, etc. are used at present. However,along with refinement disconnection in the via has resulted in a problemsuch as by an electro-migration phenomenon. Instead of the copperwirings, in a case where vertical wirings are replaced with thevertically aligned single-walled carbon nanotube bulk structureaccording to the invention, or the aligned single-walled carbon nanotubebulk structure patterned for the shape of the structure into apredetermined shape, it is possible to supply a current at a 1,000 timesdensity compared with copper and, since there is no electro-migrationphenomenon, the via wirings can be further refined and stabilized. FIG.19 schematically shows an example.

Further, the electric conductor according to the present invention orwirings formed therewith can be utilized as electric conductors orwirings for various articles, electric products, electronic products,optical products, and mechanical products.

For example, the vertically aligned single-walled carbon nanotube bulkstructure or the aligned single-walled carbon nanotube bulk structure inwhich the shape of the structure is patterned into a predetermined shapeaccording to the present invention can provide refinement andstabilization by using them instead of lateral copper wirings in thelayer due to the superiority in view of high electroconductivity andmechanical strength.

(D) Optical Element (Optical Property)

While calcite crystals have been used so far for optical elements, forexample, a polarizer, since this is extremely large and expensiveoptical part and does not function effectively in an ultra shortwavelength region which is important in the next generation lithography,a single-walled carbon nanotube as a single element has been proposed asa substitution material. However, this involves a problem of difficultyin highly aligning the elemental single-walled carbon nanotube andpreparing a micro-aligned film structure having light transmittance.Since the vertically aligned single-walled carbon nanotube bulkstructure or the aligned single-walled carbon nanotube bulk structure inwhich the shape of the structure is patterned in the a predeterminedshape according to the present invention shows a super alignmentproperty, the thickness of the aligned thin film can be controlled bychanging the pattern of a catalyst and the light transmittance of thethin film can be controlled strictly, this shows an excellentpolarization property in a wide wavelength range from the ultra shortwavelength region to the infrared region when used as the polarizer.Further, since the ultra thin carbon nanotube aligned film functions asan optical element, the size of the polarizer can be miniaturized andFIG. 20 schematically shows an example of the polarizer.

The optical device according to the present invention is not restrictedto the polarizer but can be applied as other optical devices byutilizing the optical property thereof.

(E) Strength Reinforcing Material (Mechanical Property)

Heretofore, carbon fiber reinforced materials have a strength 50 timesas large as aluminum and have been used generally as a material light inweight and having strength for example, in airplane parts and sportsgoods but further reduction in the weight and increase in the strengthhave been demanded strongly. Since the aligned single-walled carbonnanotube bulk structure or the aligned single-walled carbon nanotubebulk structure in which the shape is patterned into the predeterminedshape according to the present invention has a strength several tenstimes as much as the existent carbon fiber reinforcing materials,products of extremely high strength can be obtained by utilizing thebulk structures instead of the existent carbon fiber reinforcingmaterials. Since the reinforcing materials have reduced in weight andhigh strength, as well as have characteristics such that they have highresistance to thermal oxidation (up to 3,000° C.), flexibility, electricconductivity, and electric wave shielding property, are excellent inchemical resistance and corrosion resistance, favorable in wear/creepproperty, excellent in wear resistance and vibration damping property,they can be utilized in the fields requiring reduced weight and strengthincluding airplanes, sports goods, and automobiles. FIG. 21 is a viewshowing electron microscopic (SEM) photographic images of the processfor producing reinforced single-walled carbon nanotube fibers using analigned single-walled carbon nanotube bulk structure and a producedreinforced single-walled carbon nanotube fibers.

The reinforcing materials of the invention can be blended with basematerials such as metals, ceramics, or resins into composite materialsof high strength.

(F) Super Capacitor, Secondary Battery (Electric Property)

Since a super capacitor stores energy by migration of charges, it has afeature capable of flowing a large current, enduring charge/dischargeexceeding 100,000 cycles, and showing short charging time. An importantperformance as the super capacitor is that the static capacitance islarge and the internal resistance is low. The static capacitance isdetermined by the size of pores (holes) and it has been known to bemaximum at the order of 3 to 5 nanometer referred to as meso-pores,which agrees with the size of a single-walled carbon nanotubesynthesized by water addition method. Further, in a case of using thealigned single-walled carbon nanotube bulk structure or the alignedsingle-walled carbon nanotube bulk structure in which the shape of thestructure is patterned into a predetermined shape according to thepresent invention, since all the constituent elements can be optimizedin parallel and the surface area of the electrode, etc. can bemaximized, the internal resistance can be minimized, so that a supercapacitor of high performance can be obtained.

FIG. 22 schematically shows an example of a super capacitor using, as aconstituent material or an electrode material, the vertically alignedsingle-walled carbon nanotube bulk structure, or the alignedsingle-walled carbon nanotube bulk structure in which the shape of thestructure is patterned into a predetermined shape according to thepresent invention.

The aligned single-walled carbon nanotube bulk structure according tothe present invention can be applied not only to the super capacitor,but also to the constituent material for usual super capacitors, as wellas electrode material for secondary batteries such as a lithium cell,electrode (negative electrode) material for fuel cell or air cell.

(G) Gas Storage Material/Absorbent (Absorbancy)

It has been known that the carbon nanotube shows gas absorbancy tohydrogen or methane. Then, it can be expected for the alignedsingle-walled carbon nanotube according to the present invention havingparticularly large specific surface area to be applied to storage andtransportation of a gas such as hydrogen or methane. FIG. 23schematically shows a conceptional view in a case of applying thealigned single-walled carbon nanotube bulk structure according to thepresent invention as a hydrogen storage storage material. Further, itcan absorb a noxious gas or substance and separation and purify the gasor the substance like an activated carbon filter.

EXAMPLE

Hereinafter, it will be described the present invention in more detaileby way of examples. As a matter of course, the present invention is notrestricted to the following examples.

Example 1

A carbon nanotube was grown by CVD method under the followingconditions.

Carbon compound: ethylene; feed rate at 50 sccm

Atmosphere (gas)(Pa): helium, hydrogen gas mixture; feed rate at 1,000sccm

Pressure: 1 atm

water vapor addition amount (ppm): 300 ppm

Reaction temperature (° C.): 750° C.

Reaction time (min): 10 min

Metal catalyst (existent amount): iron thin film; 1 nm thickness

Substrate: silicon wafer

The catalyst was disposed on a substrate by using a sputtering vapordeposition apparatus and vapor depositing an iron metal to a thicknessof 1 nm.

A relation between the reaction time and the growth state of thevertically aligned single-walled carbon nanotube (height), under theconditions described above was examined. The result is shown in FIG. 24.

Further, for the comparison, the growth state of the vertically alignedsingle-walled carbon nanotube was examined (existent CVD method) in thesame manner as described above except for not adding water vapor(existent CVD method). Results after 2 min and after 15 min are shown inFIG. 25.

As a result, the catalyst was deactivated in several seconds in a caseof growing vertically aligned single-walled carbon nanotube by theexistent CVD method and the growth was stopped 2 min after, whereas inthe method of Example 1 with addition of water vapor, the growthcontinued for a long time as shown in FIG. 25, and continuation of thegrowth was observed actually for about 30 min. Further, it was foundthat the growth rate of the vertically aligned single-walled carbonnanotube according to the method of Example 1 was extremely higher asabout 100 times of the existent method. Further, intrusion of thecatalyst or amorphous carbon was not recognized in the verticallyaligned single-walled carbon nanotube according to the method of Example1, and the purity thereof was 99.98 mass % in a not-purified state. Onthe other hand, for the vertically aligned carbon nanotube obtained bythe existent method, an amount that could be measured for the puritycould not be obtained. Based on the result, superiority due to theaddition of water vapor was confirmed regarding the growth of thevertically aligned single-walled carbon nanotube in the CVD method wasconfirmed.

Example 2

A carbon nanotube was grown by CVD method under the followingconditions.

Carbon compound: ethylene; feed rate at 100 seem Atmosphere (gas):helium, hydrogen gas mixture; feed rate at 1,000 sccm

Pressure: 1 atm

Water vapor addition amount (ppm): 175 ppm

Reaction temperature (° C.): 750° C.

Reaction time (min): 10 min

Metal catalyst (existent amount): iron thin film; 1 nm thickness

Substrate: silicon wafer

The catalyst was disposed on a substrate by using a sputtering vapordeposition apparatus and vapor depositing an iron metal to a thicknessof 1 nm.

FIG. 26 shoes images formed by printing photographs, taken-up by adigital camera, of vertically aligned single-walled carbon nanotubesgrown under the conditions described above. FIG. 26 shows the verticallyaligned single-walled carbon nanotubes grown to a height of about 2.5 mmat the center, a match stick on the left, and a ruler with one gradationfor 1 mm on the right.

FIG. 27 is a perspective view showing electron microscopic (SEM)photographic images for vertically aligned single-walled carbonnanotubes grown in Example 2.

FIG. 28 shows enlarged electron microscopic (SEM) photographic imagesfor vertically aligned single-walled carbon nanotubes grown in FIG. 2.From FIG. 28, it can be seen the state where the vertically alignedsingle-walled carbon nanotubes at a height of 2.5 mm are alignedvertically at a super high density.

FIG. 29 and FIG. 30 show photographic images of the vertically alignedsingle-walled carbon nanotubes by peeling them from a substrate usingtweezers, dispersing them in an ethanol solution and placing them on agrid of an electron microscope (TEM) and observing them by the electronmicroscope (TEM). It can be seen that the obtained carbon nanotubes aresingle-walled. Further, it can be seen that neither catalyst noramorphous carbon is intruded at all in the grown substance. Thesingle-walled carbon nanotubes in Example 2 were at 99.98 mass % in anot purified state. For comparison, FIG. 31 shows ideal electronmicroscopic (TEM) photographic images of as-grown single-walled carbonnanotubes prepared by an existent CVD method with no addition of watervapor. In FIG. 31, black spots show catalyst impurities.

FIG. 32 shows the result of thermogravimetric analysis for thevertically aligned single-walled carbon nanotubes produced in Example 2.TGD-900 manufactured by ULBAC Inc. was used as an analyzer. It can beseen from the portion shown at A in the graph that the reduction ofweight at a low temperature is small and no amorphous carbon is present.It can be seen from the portion shown at B in the graph that thecombustion temperature of the single-walled carbon nanotube is high andthe quality is high (high purity). It can be seen that from the portionshown at C in the graph that residues are not contained.

Further, impurity measurement was carried out by fluorescence X-rays forthe vertically aligned single-walled carbon nanotubes produced inExample 2. As a result, only the impurity element Fe as the catalyst wasdetected by 0.013 mass %, and other impurities were not detected.Further, iron impurities were mixed in the cellulose used forimmobilization to an extent identical with that in the verticallyaligned single-walled carbon nanotubes in Example 2 and it is estimatedthat the actual purity of the vertically aligned single-walled carbonnanotubes in Example 2 was further higher. Further, as comparison, whenimpurity measurement was carried out by identical fluorescence X-raysalso for the vertically aligned single-walled carbon nanotubes producedby the existent CVD method and the vertically aligned single-walledcarbon nanotubes produced by the HiPco method, the impurity element Fewas detected by 17 mass % for those by the existent CVD method and theimpurity Fe was detected by 30 mass % for those by the HiPco method.

Example 3

A carbon nanotube was grown by CVD method under the followingconditions.

Carbon compound: ethylene; feed rate at 75 sccm

Atmosphere (gas): helium, hydrogen gas mixture; feed rate at 1,000 sccm

Pressure: 1 atm

Water vapor addition amount (ppm): 400 ppm

Reaction temperature (° C.): 750° C.

Reaction time (min): 10 min

Metal catalyst (existent amount): iron thin film; 1 nm thickness

Substrate: silicon wafer

The catalyst was disposed on a substrate by using a sputter vapordeposition apparatus and vapor depositing an iron metal to a thicknessof 1 nm.

The peeling property of the vertically aligned single-walled carbonnanotubes produced as described above was examined. Peeling wasconducted by using tweezers.

FIG. 33 shows a state of vertically aligned single-walled carbonnanotubes before peeling taken-up by a digital camera, FIG. 34 shows astate after peeling and FIG. 35 shows as-grown single-walled carbonnanotube purification products (30 mg) peeled and placed in a vessel. Asthe result of the peeling test, it was confirmed that the verticallyaligned single-walled carbon nanotubes produced by the method of theinvention were peeled easily.

Example 4

A vertically aligned single-walled carbon nanotube bulk structure wasgrown by a CVD method under the following conditions.

Carbon compound: ethylene; feed rate at 75 sccm

Atmosphere (gas): helium, hydrogen gas mixture; feed rate at 1,000 sccm

Pressure: 1 atm

Water vapor addition amount (ppm): 400 ppm

Reaction temperature (° C.): 750° C.

Reaction time (min): 10 min

Metal catalyst (existent amount): iron thin film; 1 nm thickness

Substrate: silicon wafer

The catalyst was disposed on a substrate as described below.

An electron beam exposure resist ZEP-520A was appended thinly on asilicon wafer by a spin coater at 4,700 rpm for 60 sec and baked at 200°C. for 3 min. Then, by using an electron beam exposure apparatus, acircular pattern of 150 μm diameter was formed at a 250 μm pitch on theresist-appended substrate. Then, by using a sputtering vapor depositionapparatus, iron metal was vapor deposited to 1 nm thickness and,finally, the resist was peeled by a peeling solution ZD-MAC from thesubstrate, to prepare a silicon wafer to which the catalyst metal waspatterned optionally.

Under the conditions described above, an assembly of vertically alignedsingle-walled carbon nanotubes patterned into a circular cylindricalshape was obtained. FIG. 36 shows the shape of the assembly as imagestaken-up by an electron microscope (SEM) and FIG. 37 and FIG. 38 showimages for the state of the base of the assembly taken-up by an electronmicroscope (SEM). It can be confirmed from FIG. 38 that thesingle-walled carbon nanotubes are aligned in plurality in the verticaldirection at a super high density.

Example 5

An aligned single-walled carbon nanotube bulk structure was grown by aCVD method under the following conditions.

Carbon compound: ethylene; feed rate at 75 sccm

Atmosphere (gas): helium, hydrogen gas mixture; feed rate at 1,000 sccm

Pressure: 1 atm

Water vapor addition amount (ppm): 400 ppm

Reaction temperature (° C.): 750° C.

Reaction time (min): 10 min

Metal catalyst (existent amount): iron thin film; 1 nm thickness

Substrate: silicon wafer

The catalyst was disposed on a substrate as described below.

An electron beam exposure resist ZEP-520A was appended thinly on asilicon wafer by a spin coater at 4,700 rpm for 60 sec and baked at 200°C. for 3 min. Then, by using an electron beam exposure apparatus toprepare a pattern of 3 to 1,005 μm thickness, 375 μm to 5 mm length, and10 μm to 1 mm pitch. Then, by using a sputtering vapor depositionapparatus, iron metal was vapor deposited to 1 nm thickness and,finally, the resist was peeled by a peeling solution ZD-MAC from thesubstrate, to prepare a silicon wafer to which the catalyst metal waspatterned optionally.

FIG. 39 to FIG. 43 show five examples of vertically alignedsingle-walled carbon nanotube bulk structure produced by changing thepatterning of the catalyst and the reaction time by electron microscopic(SEM) photographic images. It can be seen that the structure in FIG. 39is a thin film structure of 5 μm thickness and has flexibility. FIG. 40is a view showing a plurality of thin film structures from the lateralside and it can also be seen that it has flexibility. FIG. 41 shows aplurality of thin film structures arranged in a complex state. FIG. 42shows a thin film structure of different thickness with the currentthickness of 3 μm at the minimum and those of larger thickness canoptionally be controlled by the patterning of the catalyst. FIG. 43shows a structure of a complicate shape. Further, FIG. 44 shows anexample of the aligned structures as images observed from the frontalside by an electron microscope (SEM), and FIG. 45 shows images for thecorner of one example of the aligned structures observed by an electronmicroscope (SEM). From each of them, it can be seen that thesingle-walled carbon nanotubes are aligned.

Example 7 Super Capacitor

For the evaluation of the characteristics of the vertically alignedsingle-walled carbon nanotube bulk structure obtained in Example 2 as acapacitor electrode, 2.917 mg of an aligned single-walled carbonnanotube bulk structure was bonded with a conductive adhesive as anoperation electrode on an Al plate as shown in FIG. 46 and anexperimental cell was assembled. TEABF₄/PC at 1M concentration was usedas an electrolyte. The constant current charge/discharge characteristicof the thus manufactured experimental cell was measured. FIG. 47 showsthe result. It can be seen from charge/discharge curves of FIG. 47 thatthe aligned single-walled carbon nanotubes operated as a capacitormaterial, the internal resistance was low and the capacitance wassubstantially constant and not lowered even upon high ratecharge/discharge (high current density).

Example 8 Lithium Ion Cell (Secondary Battery)

2.4 mg of the aligned single-walled carbon nanotube bulk structureobtained in Example 2 was used as the operation electrode. Lithium wasused for the counter electrode and the reference electrode. Stainlesswas used for the collector and the battery was assembled by using thecell of commercial products manufactured by Hohsen Corp. LiBF₄/EC:DEC(1:1) at 1M was used as the electrolyte and charge/dischargecharacteristic was evaluated at a current density of 20 mA/g. FIG. 48shows the result. From FIG. 48, extremely large irreversiblecharge/discharge was observed in the first cycle of discharge.Occurrence of large charge at an extremely stable potential suggeststhat intercalation of lithium occurs in the aligned single-walled carbonnanotube bulk structure. Stable charge/discharge characteristics wereobtained at and after the second cycle and the operation as the batterywas confirmed. It can be seen that the aligned single-walled carbonnanotube bulk structure can be used as the electrode material for thesecondary battery.

Example 9

For 50 mg of the aligned single-walled carbon nanotube bulk structureobtained in Example 2, adsorption/desorption isothermal curves forliquid nitrogen were measured at 77 using BELSORP-MINI of Bel Japan Inc.(adsorption equilibrium temperature was 600 sec). The entire adsorptionamount showed an extremely large numerical value (1,650 m²/g). When thespecific surface area was measured from the adsorption/desorptionisothermal curves, it was 1,100 m²/g.

Further, 50 mg portion was torn from the identical aligned single-walledcarbon nanotube bulk structure by tweezers, disposed evenly on analuminum tray, and placed in a muffle furnace. Then, temperature waselevated up to 550° C. at 1° C./min and a heat treatment was conductedat 550° C. for one min in oxygen (20% concentration). The weight of thesample after the heat treatment was 43 mg and remaining 7 mg was burntout. In the same manner as described above, the adsorption/desorptionisothermal curves of liquid nitrogen were measured for the sample afterthe heat treatment (FIG. 49). As a result, when the specific surfacearea was estimated, it was about 2,000 m²/g. The sample after the heattreatment had a large specific surface area compared with the as-grownsample and it was suggested that the top ends of the carbon nanotubeswere opened by the heat treatment. In the graph, P represents anadsorption equilibrium pressure and P_(o) represents a saturated vaporpressure. The as-grown not-opened single-walled carbon nanotubes (FIG.6) show a high linearity for the adsorption/desorption isothermal curvesof liquid nitrogen in a low relative pressure region of 0.5. On theother hand, the adsorption/desorption isothermal curves of the openedsingle-walled carbon nanotube (FIG. 49) are characterized by a largeinitial adsorption rising and by convex adsorption/desorption isothermalcurves at a large adsorption amount in a relative pressure region of 0.5or lower. The convex-adsorption/desorption isothermal curves are shownbecause adsorption occurs at the inner surface and the outer surface inthe opened carbon nanotubes. As described above, by measuring theadsorption/desorption isothermal curves, it can be distinguished whetherthe carbon nanotubes are not opened or opened.

Example 10 Polarizer

The polarization dependency of light transmittance was measured by usingthe aligned single-walled carbon nanotube bulk structure obtained inExample 4. A sample of 300 nm thickness was used and measurement wascarried out by using a helium/neon laser as a light source and using aλ/2 Fresnel rhomb wavelength plate, an objective lens, and a light powermeter. A laser light at 633 nm emitted from the light source wascontrolled for the intensity by using an ND filter and then condensed byusing an optical lens to the surface of the aligned single-walled carbonnanotube bulk structure sample. The laser light transmits the alignedsingle-walled carbon nanotube bulk structure as the sample, condensed byusing another objective lens and then guided to the light power meter.In this case, polarization of the laser light could be controlled to anoptional direction by using a wavelength plate. The result is shown inFIG. 50.

It could be confirmed from the result of FIG. 50 for the utilization ofthe aligned single-walled carbon nanotube bulk structure to thepolarizer.

Further, the absorbancy of the sample was calculated based on theintensity of transmission light at each polarized light detected by thelight power meter. The result is shown in FIG. 51. In this case, 0degree is the aligning direction and 90 degree is a direction verticalto the aligning direction. It can be seen from FIG. 51 that the extentof the anisotropy of the light adsorbancy in the aligning directionrelative to the light absorbency in the direction vertical to thealigning direction is larger than 1:10.

Example 11 Gas Storage

For 100 mg of the aligned single-walled carbon nanotube bulk structureobtained in Example 2, measurement was carried out for hydrogen storageby using a high pressure mono-ingredient adsorption amount measuringapparatus (FMS-AD-H) manufactured by Bel Japan Inc. As a result, thestorage amount of hydrogen was 0.54% by weight at 10 MPa, 20° C.Further, also in the releasing process, it was detected that reversiblerelease depending only on the pressure was detected. The measuringresult is shown in FIG. 52.

Example 12 Heat Conductor/Heat Dissipation Material

For the aligned single-walled carbon nanotube bulk structure obtained inExample 2, heat diffusion ratio was measured by a laser flash method forexamining the heat conductivity. The measuring temperature was at a roomtemperature and the specimen size was 1 cm square. Measurement wascarried out in three kinds of forms, i.e., a sample per se, and glassplates placed above or below the sample. The heat diffusion ratio wasdetermined by a CF method and zero extrapolation for the pulse heatingenergy dependency. FIG. 53 shows examples of the results of measurement.In FIG. 53, (a) is measured data in vacuum, (b) is measured data inatmospheric air, the abscissa indicates time, and the ordinate indicatesthe specimen temperature. As the result of measurement for the specimenper se in vacuum, the thermal diffusivity α is 8.0×10⁻⁵ m²s⁻¹. Whenseveral samples were measured, the thermal diffusivity a was within arange from 7.0×10⁻⁵ to 1.0×10⁻⁵ m²s⁻¹ even when the measuring conditionswere changed. Thus, favorable heat conductivity was confirmed.

Further, in vacuum, the sample temperature was substantially constantwith less effect of heat loss, and, in atmospheric air, lowering of thesample temperature was obtained to show that the effect of heat loss waslarge. From the foregoings, the heat dissipation effect of the alignedsingle-walled carbon nanotube bulk structure could be confirmed.Accordingly, it can be expected that the aligned single-walled carbonnanotubes can be utilized as the heat conductor and the heat dissipationmaterial.

Example 13 Electric Conductor

The aligned single-walled carbon nanotube bulk structure obtained inExample 2 was formed into 1 cm×1 cm×1 mm height shape, copper plateswere in contact with both sides thereof and the electric transportingcharacteristic was measured by 2-terminal method using a prober ofSumit-12101B-6 manufactured by Cascade Microtech Japan Inc. and asemiconductor analyzer (4155C) manufactured by Agilent Co. The result isshown in FIG. 54. From FIG. 54, it can be seen that current shows aclear ohmic dependency to voltage (amplifier of the prober reachedsaturation at a current value of 0.1 A). The measured resistance valuewas 6Ω. The resistance value includes two kinds, i.e., the conductionresistance through the aligned single-walled carbon nanotube bulkstructure and the contact resistance of the aligned single-walled carbonnanotube bulk structure and the copper electrode, showing that thealigned single-walled carbon nanotube bulk structure and the metalelectrode can be brought into close contact at a small contactresistance. From the foregoings, it can be expected that the alignedsingle-walled carbon nanotube bulk structure that it can be used as theelectric conductor.

1-106. (canceled)
 107. A single-walled carbon nanotube having a specificsurface area of between 800 m²/g or more and 2500 m²/g or less; andhaving a purity measured by fluorescence X-rays of 98% or more.
 108. Thesingle-walled carbon nanotube according to claim 107, having a centersize of 1 to 4 nm.
 109. The single-walled carbon nanotube according toclaim 108, having a center size of 1.5 to 4 nm.
 110. The single-walledcarbon nanotube according to claim 107, wherein the single-walled carbonnanotube has a specific surface area of between 800 m²/g or more and1300 m²/g or less, and is not open.
 111. The single-walled carbonnanotube according to claim 107, wherein the single-walled carbonnanotube has a specific surface area of between 1600 m²/g or more and2500 m²/g or less, and is open.